Guidelines for dopant selection in Cu catalysts to promote the electrochemical CO2 reduction reaction for ethylene production

Our study proposed that a dopant with a low standard reduction potential is difficult to reduce, which leads to a stable Cu δ + species, enhancing CO 2 RR catalytic activity. To develop an efficient electrochemical CO 2 reduction reaction (CO 2 RR) for the production of C 2 chemicals, improvements in the Cu catalyst are necessary. Doping is widely used for catalyst enhancement; however, only a few elements have been examined. This study proposes guidelines for the selection of Cu catalyst dopants to promote ethylene production. It was hypothesized that the dopant chemical state highly influences the CO 2 RR catalytic activity. In the case of dopants possessing a standard reduction potential within the CO 2 RR potential region (e.g., Mn and Ni), low Faradaic efficiency (FE) toward ethylene production was obtained owing to the presence of a metallic dopant (10.7% for Ni dopant). In contrast, a low standard reduction potential led to a stable high oxidation state for the dopant, yielding abundant Cu δ + species with modified electronic structures and enhancing the CO 2 RR catalytic activity for ethylene production (42.1% for Hf dopant). We expected that a dopant with a low standard reduction potential is difficult to reduce, which leads to a stable Cu–O–X bond and induces a stable Cu δ + species. Our study provides insights into how to select dopant for various catalyst to enhance CO 2 RR catalytic activity.